The genome of rotaviruses, members of the reoviridae family, consists of 11 discrete segments (genes) of dsRNA. Its unusual genome structure (segmentation) and the relative ease of generation of reassortants in vitro have provided a unique opportunity to gain insight into genetic and molecular mechanisms of virus-host interactions through mapping of biological function of specific genes. During the past year, efforts were made to generate single gene substitution human x human rotavirus reassortants which would be potential human rotavirus vaccines. In addition, antigenic analysis of VP3 (the fourth gene product) and VP7 (the eighth or ninth gene product) of rotavirus was performed.